ROLLER COMPACTED CONCRETE

DESIGN AND CONSTRUCTION FOR INTERMODAL TERMINALS

James N. McLeod, P.Eng. Adam Laughlin, EIT

Regional Manager - Rail Project Engineer

Telephone: (780) 486-7000

Fax: (780) 486-7070

UMA Engineering Ltd.

17007 - 107 Avenue

Edmonton, Alberta

Canada, T5S 1G3

TABLE OF CONTENTS

Introduction - Project Overview

Roller Compacted Concrete

- Overview

- Mixing, Placement, Compaction and Curing

- RCC Pavement Design

- Site Specific Cost Comparison

- Construction Summary

Bonding RCC Layers - Testing and Evaluation

Conclusion

LIST OF TABLES

Table 1 - Cost Comparison

Table 2 - Roller Compacted Concrete - Pavement Test Area - Core Sample Results

LIST OF FIGURES

Figure 1 - Consolidation and Bond Test Locations

Figure 2 - Edmonton Intermodal Terminal - Construction Sequence

Figure 3 - Fantuzzi Rail Stacker Crane in Operation

Figure 4 - RCC Mixing Plant in Operation

Figure 5 - RCC Paving Operation

Figure 6 - RCC Base Lift Surface Scarification After Rolling

Figure 7 - Top Lift Placement

Figure 8 - RCC Placement Adjacent to New Track

Figure 9 - RCC Surface Scarification Between Layers (foreground) / Roller Compaction

(background)

Figure 10 - RCC SS-1 Curing Compound Application

Figure 11 - RCC Surface with Tack Coat Curing

ABSTRACT

Roller Compacted Concrete Design and Construction for Intermodal Terminals

With the tremendous growth in intermodal traffic, railways need to fast track the expansion or

replacement of existing intermodal transfer facilities. This report describes the pavement design and

construction for Canadian National’s (CN) new intermodal terminal in Edmonton, Alberta that

opened on time and on budget, October 2nd, 2001.

The new terminal is strategically located between two mainline subdivisions and is adjacent to

excellent highway truck access. The location can also accommodate extensive future expansion.

To support the significant wheel loads generated during container transfer operations, various

pavement structures were evaluated. The use of roller compacted concrete (RCC) was selected to

meet structural requirements and balance design economy with an extremely tight timeline to

construct. The pavement structure consists of 2 – 8 inch lifts of RCC over a 10 inch compacted

granular base. The paper will also describe the previous field-testing undertaken to evaluate and

improve surface bond between RCC layers. As a result of these tests, a light surface scarification of

the base layer of RCC was incorporated into the construction sequence with excellent results. In

total, over 110,000 square yards of RCC pad was placed in just under 30 days.

INTRODUCTION - PROJECT OVERVIEW

Intermodal traffic comprises containers that move from origin to destination by a combination of

truck, train and ship. With significant ongoing and projected growth in intermodal traffic, CN’s

existing intermodal terminal in Edmonton, Alberta, Canada had essentially reached full operating

capacity with no viable option for further expansion.

In 1999, CN embarked on a 3 phase, 30 year strategic plan for the staged development of a new

intermodal rail terminal to be located in northwest Edmonton. The new facility is strategically

located to provide excellent roadway and rail access, with the Yellowhead Highway to the south and

the terminal situated between two mainline subdivisions. In addition, the development of this

facility presented an opportunity to relocate the existing terminal from a developed area, resulting in

a reduction in truck traffic and related operational noise through an adjacent residential community.

In consideration of this, the design of the new terminal incorporated a depressed terminal grade line

as well as berming along the east side of 184 Street to mitigate potential future noise and visual

impact concerns.

The terminal layout consists of a central roller compacted concrete (RCC) pad between 7,500 feet

(2,300 m) long pad tracks that connect to the mainline tracks at each end of the terminal. The RCC

pad accommodates the rail stacker crane used to transfer containers between rail cars and trucks.

To support the significant wheel loads from the stacker crane operation a 16 inch (400 mm) RCC

pad thickness (placed in 2 – 8 inch (200 mm) lifts) over a 10 inch (250 mm) granular subbase was

selected. To enhance the bond between lifts an innovation developed by UMA incorporated a light

surface scarification immediately in advance of the second lift.

Site drainage utilizes an on-site stormwater management pond that collects all drainage from the site

for pre-treatment through an oil/water separator prior to a controlled release (to maintain desired

water levels) into the adjacent Kinokamau wetland.

Terminal Notes

Roller Compacted Concrete: 92,500 tons (94,000 tonnes) covering an area of 111,230 square yards

(93,000 m²) placed over a period of roughly 30 days between June 15, and July 14, 2001.

Track: Approximately 12 miles (19 kms) of new track constructed between April 15 and September

15, 2001.

Facility: The terminal facility built within a $25 million (CAN) overall budget included property

acquisition, environmental permitting, detailed design, site engineering, grading, drainage, RCC pad,

trackage, asphalt roadways, automated entrance gate, operations center, maintenance facility,

communications, yard air and lighting.

Transfer of Services to CN Operations: September 29-30, 2001.

Grand Opening: October 2, 2001.

ROLLER COMPACTED CONCRETE

Overview

Roller compacted concrete (RCC) consists of the same material components, i.e. Portland cement,

fly ash (optional), coarse to fine aggregate and water, and is designed to achieve equivalent or higher

compressive and flexural strengths to that of conventional concrete pavements. The RCC is placed

at zero-slump through a paver and is compacted in place with a vibratory roller (similar to an asphalt

paving operation). This method of placement allows for a large amount of concrete to be placed

quickly without the need for forms, dowels or reinforcing steel. Significant cost savings can be

realized by combining the inherent efficiencies of this paving technique with the final product of a

rigid, high strength Portland cement concrete pavement. The RCC pavement surface however is

generally rougher than conventional concrete pavement which has tended to limit its application to

terminals and load out facilities accommodating heavily loaded vehicles travelling at low speeds.

RCC pavements have been used for streets and highways but these applications generally require an

asphalt overlay to improve surfacing and ride quality characteristics.

Mixing, Placement, Compaction and Curing

RCC is typically mixed on site in a continuously mixing pugmill plant. The aggregate and cement is

proportioned on conveyor belts and fed into the pugmill where they are mixed with the relatively

small amount of water necessary to produce a stiff, zero-slump concrete. The freshly mixed RCC is

collected into a small hopper and deposited into end-dump trucks for transport to the paver.

The RCC is placed with a paving machine onto a compacted base course over a prepared subbase

surface. Immediately after placement, the RCC is compacted to specified densities with a dual-drum

vibratory steel roller. The maximum thickness of a lift of RCC is generally limited by the paver

capacity and the ability of the rollers to effectively compact through the full depth of the layer. The

maximum uncompacted thickness is therefore usually about 10 inches (250 mm), with a compacted

final thickness of between 8 to 9 inches (200 – 225 mm). For thicker pavements, 2 or 3 layers or

lifts of RCC may be required. Placing RCC in layers unfortunately creates a horizontal joint or plane

between the layers. Sufficient bond needs to be developed between these layers in order to produce

a monolithic RCC pavement structure. To achieve this, the time between placement of the next

layer needs to be as short as possible (generally less than 60 minutes, depending on ambient

conditions of temperature and humidity) so that the underlying layer is still relatively fresh and has

not set up before the next layer is placed. It should be noted that although this timeline was

adhered to on an earlier project, core samples extracted showed a poor bond between layers. This

initiated a test program to evaluate alternate methods to enhance the bond between layers of RCC

(discussed in more detail in a following section).

Once placed, compaction of the RCC is accomplished by self-propelled vibratory steel wheel and

rubber tired rollers. Rolling generally commences within 10 minutes of spreading and should be

completed within 45 minutes. A rolling pattern needs to be established that will achieve the required

density with a minimum number of roller passes. The required wet field density for RCC should be

between 98-100% of the maximum wet density obtained by ASTM D1557, with no individual test

below 95%.

Once compaction has been completed the RCC pavement should be cured for a period of 7 days or

until the concrete has reached a minimum strength of 2,900 psi (20 MPa). Water curing or the

application of a specified asphalt emulsion or membrane-forming curing compound can be used to

ensure proper curing. The RCC pavement should be allowed to more fully cure, typically for 28

days to reach design strengths before being placed into service.

RCC Pavement Design

In order to accommodate the heavy wheel loads associated with container transfer crane operations,

a rigid pavement structure is generally recommended. As indicated, the use of RCC was selected to

meet these structural requirements and balance design economy with an extremely tight timeline to

construct. The proposed stacker crane used for this design is a Fantuzzi RS-50 (RS-70 also

evaluated) with a front axle weight of 254,000 lbs (1131 kN) when fully loaded.

The RCC thickness design was undertaken using the method described in “Structural Design of

Roller-Compacted Concrete for Industrial Pavements” developed by the Portland Cement

Association. This design was compared with results obtained using software developed for

Concrete Thickness Design for Airport and Industrial Pavements, also developed by the Portland

Cement Association. The results varied somewhat based on the parameters used but were generally

found to be consistent. The WinPAS Pavement Analysis Software (based on the 1993 AASHTO

Guide Procedure for the Design of Pavement Structures) was also investigated but this procedure

was not used, as the results are not considered to be valid for rigid pavements greater than 12.5

inches (320 mm) thick.

The design considered a subgrade California Bearing Ratio (CBR) of 3.5% with a ¾ in (20 mm)

minus well graded crushed gravel base course compacted to 100% Standard Proctor Density at or

near optimum moisture content. The RCC was required to have a minimum flexural strength of 700

psi (4.8 MPa), equating to 5,000 psi (34.5 MPa) compressive strength concrete.

With due consideration to paver and compaction depth limitations and to avoid the extra cost

associated with a third lift, an RCC final pavement thickness of 16 inches (400 mm) made up of 2 –

8 inch (200 mm) lifts, over a 10 inch (250 mm) compacted granular base on the prepared subbase

was ultimately selected.

Site Specific Cost Comparison

Once the RCC pavement design had been established, a cost comparison with other equivalent

pavement structures was undertaken prior to proceeding with the final recommendation for RCC

pavement (see Table 1). Although it should be emphasized that these cost comparisons are only

valid for this specific project (owing to local material costs, aggregate availability and subgrade

conditions), the RCC pavement was found to be the least cost alternative as compared with

equivalent pavement structures using asphalt pavement or conventional cast-in-place concrete.

Construction Summary

With the required environmental permitting in place, initial site grading commenced in September of

1999. The site grading also included the stockpiling of alumina and silica rich clay for use in the

manufacture of cement (part of the property acquisition arrangements with the previous landowner).

Site drainage construction followed, incorporating on-site storage for stormwater management with

pre-treatment (through an oil/water separator) prior to discharge into the adjacent wetland. A

control structure was also constructed for ultimate discharge into the City’s storm sewer system.

With preliminary site work complete, the bulk of the terminal construction was undertaken between

May and September 2001. Work completed during this period included:

• final site grading and subbase preparation;

• roadbed and track construction;

• RCC pad, granular storage areas and asphalt access roads;

• office and equipment garage facilities; and

• utility installation, yard air, power, lighting, water and communications.

As mentioned, RCC placement of 92,500 tons of material covering an area of 111,230 square yards

was placed over a period of 30 days between June 15 and July 14, 2001.

BONDING RCC LAYERS – TESTING AND EVALUATION

The primary application of RCC has been for concrete gravity dam construction involving the

placement of RCC in continuous 18 – 20 inch (450 – 500 mm) layers to a final height of 5 to 10 feet

(1.5–3 m). The common method to achieve adequate bond between the layers in this mass concrete

application is to clean the concrete by wet sandblasting, high-pressure air or water jet blasting prior

to placing the subsequent lift. To avoid loosening aggregate and/or loosing good material, this

cleaning operation is done after the initial concrete set (1 – 3 hours depending on temperature and

humidity). For structural concrete like RCC pavement it is critical that the entire lift be fully

consolidated through proper compaction and that adequate bonding between layers is achieved.

Although pavers of today can accommodate placement of RCC in uncompacted layers of 10 – 12

inches (250 – 300 mm), core samples have shown reduced consolidation in the bottom couple of

inches in these maximum depth lifts. It is generally accepted that sufficient bond can be developed

at the horizontal interface providing the bottom lift has not reached initial set, however, this initial

set time can vary from just a few minutes to up to 60 minutes, making it difficult to place the next

lift before the bottom lift has started to set. If the top lift cannot be placed while the bottom lift is

still fresh, it is recommended that a cement slurry be used as a bonding agent prior to placement of

the next lift.

Although the time between lifts was limited to less than 60 minutes for a previously completed RCC

project, core samples extracted still often came out in two pieces, with no appreciable bond between

lifts. Segregation was also evident in the bottom 1 – 2 inches (25 – 50 mm). In light of this and

prior to undertaking the Edmonton Intermodal Project, a test program was initiated to evaluate

various methods for improving RCC consolidation and bonding.

The test program undertaken in 2000 at CN’s Sarcee Intermodal Facility in Calgary, Alberta covered

an area of 2,700 square yards (2,268 m²) and provided an opportunity to evaluate different RCC

placement methods, with and without vibration through the paver, and investigate different

techniques to improve the bond between lifts. In addition to the application of a cement slurry

between lifts, a light surface scarification (less than one-half inch (5 mm)) on the surface of the base

lift was also investigated. Figure 1 is a plan of the test locations and Table 2 is a summary of the

core samples extracted from this pavement after 28 days.

Although the tests were far from conclusive, a number of observations were made that were

beneficial in the development of the RCC specifications for the Edmonton Intermodal Project. The

difference between areas where vibration was applied and where it wasn’t did not appear to effect

the overall product; generally the concrete strengths were met or exceeded with good consolidation

evident throughout. Vibration through the paver for each lift was subsequently specified for the

RCC placement at Edmonton.

As for improving the bond between lifts, it was noted that although the bond was generally good

where the cement slurry was used (with the exception of core #2), the difficulty in being able to

apply the slurry in a uniform manner and the additional labour effort associated with this work was

felt to limit its effectiveness. It was also noted that it was more difficult to rollout the top lift of

RCC over the area with the cement slurry as the mat tended to slip along the surface of the slurry.

Alternately, good bond results were found where a light surface scarification was applied to the

bottom lift prior to placing the top lift. For the test section this was achieved with the blade of a

motor grader lightly scarping across the surface. It is believed that this light scarification tended to

break the surface glazing caused by the roller, providing a roughened surface and opportunity for

enhanced bonding. Although the method used to achieve this scarification was thought to require

further refinement, the concept was adopted for the Edmonton Project with excellent results.

CONCLUSION

The use of roller compacted concrete is a viable alternative that should be considered when

designing pavements for intermodal transfer facilities. Designs incorporating RCC pavement can be

completed quickly and realize cost savings without sacrificing pavement strength requirements. For

CN’s new Edmonton Intermodal Terminal Facility, a 16 inch (400 mm) thick RCC pavement was

able to be placed over an area in excess of 100,000 square yards in roughly 30 days.

Although RCC pavements have been around for some time, additional research and development is

still required to enhance and improve on this type of pavement structure. Results obtained from

previous work revealed a problem with obtaining proper bond between layers. Once realized, a test

was developed to evaluate different methods for improving this bond. As a result of these tests, the

implementation of surface scarification between layers was incorporated into the construction

sequence for the Edmonton project with excellent results.

After one year in operation, the RCC pavement is performing as intended under the heavy loading

and service conditions that had been anticipated.

TABLE 1 -Cost Comparison

Pavement Structure Estimated Cost

Alternative 1 RCC Pavement

16” (400 mm) RCC Pavement @ $50/m² $4,600,000

10” (250 mm) Crushed Granular Base @ $18/tonne $950,000

$5,500,000

Alternative 2 Conventional Asphalt Pavement

8” (200 mm) Asphalt @ $55/tonne $2,400,000

12” (300 mm) Crushed Granular Base @ $18/tonne) $1,150,000

16” (400 mm) Granular Subbase @ $15/tonne) $1,300,000

30” (700 mm) Granular Subbase @ $10/tonne $1,650,000

$6,500,000

Alternative 3 Conventional Concrete

12” (300 mm) Concrete @ $230/m³ $7,000,000

10” (250 mm) Crushed Granular Base @ $18/tonne $950,000

$7,950,000

Figure 1 - Consolidation and Bond Test Locations

TABLE 2 - Roller Compacted Concrete - Pavement Test Area - Core Sample Results

CN Sarcee Intermodal Terminal - August 27, 2001 (Samples tested September 24, 2001)

Specified Compressive Strength 30 MPa

Core No. Dia. (mm)

Length (mm)

Density (kg/m³)

Strength (MPa)

Remarks

1 Top 100 210 2,457 26.2

1 Bottom 100 225 2,475 35.6

Core came out in one piece with

little to no segregation evident.

2 Top 100 220 2,447 32.2

2 Bottom 100 220 2,466 37.1

Core came out in two pieces, no

bonding evident between lifts.

3 Top 100 220 2,432 35.5

3 Bottom 100 210 2,461 37.7

Core came out in one piece, some

segregation at bottom of each lift.

4 Top 100 230 2,442 37.0

4 Bottom 100 240 2,398 34.5

Core came out in two pieces, no

appreciable bond.

5 Top 100 210 2,427 34.2

5 Bottom 100 255 2,488 49.3

Core came out in one piece, very

little segregation evident.

6 Top 100 185 2,435 32.3

6 Bottom 100 255 2,463 33.5

Core came out in one piece, very

little segregation evident.

Density Conversion: 2,457 kg/m3 x .06242 = 153.3 lb/ft3

Strength Conversion: 26.2 Mpa x 145.04 = 3,800 psi

Figure 2 - Edmonton Intermodal Terminal - Construction Sequence

Figure 3 - Rail Stacker Crane

Figure 4 - RCC Mixing Plant in Operation

Figure 5 - RCC Paving Operation

Figure 6 - RCC Base Lift Surface Scarification After Rolling

Figure 7 - RCC Top Lift Placement

Figure 8 - RCC Placement Adjacent to New Track

Figure 9 - RCC Surface Scarification Between Layers (foreground) / Roller Compaction

(background)

Figure 10 - RCC - SS-1 Curing Compound Application

Figure 11 - RCC Surface with Tack Coat Curing